"Busy day planned in New York," he tweeted. "Will soon be making some very important decisions on the people who will be running our government."

According to unnamed sources quoted by the New York Times, Vice President-elect Mike Pence is to take over the job of overseeing the transition from New Jersey Governor Chris Christie because "the surprise nature of Mr Trump's victory made it critical to move more quickly to assemble a team".

The Republican is due to be inaugurated on 20 January, taking over the White House from Democrat Barack Obama, who served two terms.

'Galvanised'

Protests have taken place in US cities on both nights since the result of the election, which Mrs Clinton lost for the Democrats despite enjoying a lead in most opinion polls.

Only on Thursday, Mr Trump had tweeted: "Just had a very open and successful presidential election. Now professional protesters, incited by the media, are protesting. Very unfair!"

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Cars were damaged during the unrest in Portland

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Shop windows were broken in Oregon's largest city

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But most protests on Thursday night were peaceful. Here a protester in Los Angeles waves a dummy head of Mr Trump

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Protesters turned out again in New York

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They demonstrated outside Trump Tower in the city

About 4,000 demonstrators gathered in the centre of Portland, the largest city in Oregon, which voted in favour of Mrs Clinton.

Some protesters smashed shop and car windows, threw firecrackers and set rubbish alight. Objects were thrown at the police, who responded with pepper spray and rubber baton rounds.

Police declared a riot and made 26 arrests.

Spencer and Kristen Foxworth, who left the protest before it turned violent, told the BBC most of the demonstrators were just ordinary people like themselves who were horrified by some of the things Mr Trump stood for.

"This is not any sense of a hangover, this is more like the galvanising effect," Mr Foxworth told Outside Source. "People who were quiet, were polite or not activists by any means - I mean myself, for example - are now galvanised by this. Trump now has the Senate and the House, and there will be very little checks and balances on his actions."